France, Jan. 8 -- Greenland is vast, and highly coveted. Covering some 2 million square kilometres, it is almost four times the size of France.

Above all, it is the second-largest body of ice on Earth after Antarctica, at the opposite pole.

The ice mass is beginning to melt and could ultimately trigger a dramatic rise in sea levels. Unlike sea ice, which floats, Greenland's ice sheet lies on land. And that makes all the difference.

"In Greenland, we are dealing with extremely large masses, enormous volumes, covering the entire island," says Glenn Yannic, a lecturer and researcher at Savoie Mont Blanc University."We're talking about an ice sheet that can be several hundred metres thick. It is estimated that the complete melting of Green...